Rates of women who are opting for preventive mastectomies, such as Angeline Jolie, have increased by an estimated 50 percent in recent years, experts say. But many doctors are puzzled because the operation doesn't carry a 100 percent guarantee, it's major surgery -- and women have other options, from a once-a-day pill to careful monitoring.

As families gather for Thanksgiving this year, nearly one in three American children is living with a parent who is divorced, separated or never-married. More people are accepting the view that wedding bells aren't needed to have a family.

A study by the Pew Research Center highlights rapidly changing notions of the American family. And the Census Bureau, too, is planning to incorporate broader definitions of family when measuring poverty, a shift caused partly by recent jumps in unmarried couples living together.

Rates of women who are opting for preventive mastectomies, such as Angeline Jolie, have increased by an estimated 50 percent in recent years, experts say. But many doctors are puzzled because the operation doesn't carry a 100 percent guarantee, it's major surgery -- and women have other options, from a once-a-day pill to careful monitoring.

About 29 percent of children under 18 now live with a parent or parents who are unwed or no longer married, a fivefold increase from 1960, according to the Pew report being released Thursday. About 15 percent have parents who are divorced or separated and 14 percent have parents who were never married.Within those two groups, a sizable chunk — 6 percent — have parents who are live-in couples who opted to raise kids together without getting married.

According to the Pew survey, 39 percent of Americans say marriage is becoming obsolete. And that sentiment follows U.S. census data released in September that showed marriages hit an all-time low of 52 percent for adults 18 and over.

When asked what constitutes a family, the vast majority of Americans agree that a married couple, with or without children, fits that description. But four of five surveyed pointed also to an unmarried, opposite-sex couple with children or a single parent. Three out of five people said a same-sex couple with children is a family.

"Marriage is still very important in this country, but it doesn't dominate family life like it used to," said Andrew Cherlin, a professor of sociology and public policy at Johns Hopkins University. "Now there are several ways to have a successful family life, and more people accept them."

The broadening views of family are expected to have an impact at Thanksgiving. About nine in 10 Americans say they will share a Thanksgiving meal next week with family, sitting at a table with 12 people on average. About one-fourth of respondents said there will be 20 or more family members.

"More Americans are living in these new families, so it seems safe to assume that there will be more of them around the Thanksgiving dinner table," said Paul Taylor, executive vice president of the Pew Research Center.

The changing views of family are being driven largely by young adults 18-29, who are more likely than older generations to have an unmarried or divorced parent or have friends who do. Young adults also tend to have more liberal attitudes when it comes to spousal roles and living together before marriage, the survey found.

But economic factors, too, are playing a role. The Census Bureau recently reported that opposite-sex unmarried couples living together jumped 13 percent this year to 7.5 million. It was a sharp one-year increase that analysts largely attributed to people unwilling to make long-term marriage commitments in the face of persistent unemployment.

Beginning next year, the Census Bureau will publish new, supplemental poverty figures that move away from the traditional concept of family as a husband and wife with two children. It will broaden the definition to include unmarried couples, such as same-sex partners, as well as foster children who are not related by blood or adoption.

Officials say such a move will reduce the number of families and children who are considered poor based on the new supplemental measure, which will be used as a guide for federal and state agencies to set anti-poverty policies. That's because two unmarried partners who live together with children and work are currently not counted by census as a single "family" with higher pooled incomes, but are officially defined as two separate units — one being a single parent and child, the other a single person — who aren't sharing household resources.

"People are rethinking what family means," Cherlin said. "Given the growth, I think we need to accept cohabitation relationships as a basis for some of the fringe benefits offered to families, such as health insurance."

Still, the study indicates that marriage isn't going to disappear anytime soon. Despite a growing view that marriage may not be necessary, 67 percent of Americans are upbeat about the future of marriage and family. That's higher than their optimism for the nation's educational system (50 percent), economy (46 percent) or its morals and ethics (41 percent).

And about half of all currently unmarried adults, 46 percent, say they want to get married. Among those unmarried who are living with a partner, the share rises to 64 percent.

Other findings:

34 percent of Americans called the growing variety of family living arrangements good for society, while 32 percent said it didn't make a difference and 29 percent said it was troubling.

44 percent of people said they have lived with a partner without being married; for 30-to-49-year-olds, that share rose to 57 percent. In most cases, those couples said they considered cohabitation as a step toward marriage.

62 percent said that the best marriage is one where the husband and wife both work and both take care of the household and children. That's up from 48 percent who held that view in 1977.

The Pew study was based on interviews with 2,691 adults by cell phone or landline from Oct. 1-21. The survey has a total margin of error of plus or minus 2.6 percentage points, larger for subgroups. Pew also analyzed 2008 census data, and used surveys conducted by Time magazine to identify trends from earlier decades.

Copyright 2010 The Associated Press. All rights reserved. This material may not be published, broadcast, rewritten or redistributed.

Video: Is marriage becoming obsolete? Four in 10 say yes

>>a collaboration with the
pew research center
on the state of our union, on the state of marriage in america today. it's a study we've done over the past year. they also looked at census data of the last 50 years. the headline of the study which i'll go right to is that marriage has become an institution for the wealthier rather than the less wealthy. before
world war ii
, the
marriage rates
among people who were poorer and less educated which higher than people with more education and more money. now those lines have crossed.

>>you also say in the study that men need marriage more than
women
.

>>well, they benefit from marriage more than
women
do. they live longer, more prosperous, happier.
women
who are married aren't necessarily happier.

>>are they less happy?

>>less happy than
women
who are not married? no. more happy than
women
who are not married. more and more
women
say that marriage is not necessary to their happiness a. higher percentage of
women
say marriage is not necessary to their happiness than men say.

>>what's the basis?

>>i think men are saying it to please the
women
.

>>i'm wondering how skewed the answers are.

>>what is emerging is a
marriage gap
which is a really interesting thing. i think it's an unintentional consequence of
women
's equality which is that
once upon a time
doctors married nurses. lawyers married secretaries. now doctors mariry doctors, lawyers marry lawyers. it's keeping that income class up higher and it's separating them from lower income. it's an example of incoming equality in america. that's a whole other idea.

>>mike?

>>the incoming equality within the context of marriage, how does that play out according to this?

>>it plays out that particularly since the recession started people with less education and less income feel they can't afford to get married. marriage is more and more becoming a luxury for people who can afford it. men and
women
who have
higher education
, higher incomes than people with lower incomes.

>>why do they feel that way?

>>that i don't really know the answer to. one of the things that's very interesting is a majority of mayor cans think that marriage is obsolete. but a huge majority of americans still want to get married. something like 60% of people under 30 think marriage is obsolete.

>>how do children play into this? are people feeling comfortable having children out of wedlock does that address that issue?

>>compared to
1960
, eight times apz many out-of-wedlock births. the other thing that the pew study really saw is the notion of marriage itself -- the notion of family has changed. it's a much broader definition. single men living with children, unmarried couples living together. people consider this family. i would argue that's a good thing in the sense that family is a good thing and our definition of family has expanded.

>>i want to go off topic for one second which is we have -- the state of the magazine industry,
tina brown
who is often on this broadcast is
taking over
your competitor, "newsweek," formerly run by
jon meacham
. what do you make of this and what do you think about your own magazine?

>>i so welcome it. i think she's a fantastic
magazine editor
. she'll do a wonderful job. i think it's not an easy job. any great journalistic institution that can be revived is good for all of us.